Gear unit

ABSTRACT

A gear unit having at least one shaft supported by a bearing in the gear unit housing,
     the spatial region of a bearing of a shaft situated in a cutout of the gear unit housing being limited at least partially towards the interior of the gear unit by a limiting device, in particular one that has a cutout for a shaft supported in the bearing,   the lowest point of the cutout effecting a minimum oil level in the spatial region of the bearing.

FIELD OF THE INVENTION

The present invention relates to a gear unit.

BACKGROUND INFORMATION

It is known that gear units having oil lubrication are practicable, theoil, that is, fluid, collecting in the lower part of the interior of thegear unit when the gear unit is not in operation, that is, when thegears are at rest, where it forms the oil sump that has an oil levelcorresponding to the filling level when filling in the oil. Whenoperating the gear unit, in particular at the nominal speed of the inputshaft and/or output shaft, the toothed parts of the gear unit spray andcentrifuge the oil around. In particular, the mutually engaged toothingsalso spray out oil.

SUMMARY

Example embodiments of the present invention provide a gear unit suchthat as much power as possible is transmittable per unit volume.

Among features of example embodiments of the present invention in thegear unit are that the spatial region of a bearing of a shaft situatedin a cutout of the gear unit housing is limited at least partiallytowards the interior of the gear unit by a limiting device that has acutout for a shaft supported in the bearing,

the lowest point of the cutout effecting a minimum oil level in thespatial region of the bearing.

It is advantageous in this regard that a minimum oil level is thusensured in operation in the area of the bearings and that the latter arethus well lubricated. In the state of rest of the gear unit, a higheroil level than this minimum oil level is allowed, which is lowered whenoperating the gear unit. A very good initial lubrication of the bearingis thus provided and the losses in operation are nevertheless reducible.

In example embodiments, the spatial region is limited at least partiallyby the gear unit housing. It is advantageous in this regard that thespatial region is the region of the bearing, which is to be limitedtowards the interior of the gear unit only by the protective plate.

In example embodiments, the limiting device is a protective plate or aring. It is advantageous in this regard that a simple and cost-effectivelimitation of the spatial region is achievable.

In example embodiments, the protective plate is welded onto the housingor is connected by screws. It is advantageous in this regard that asealed connection may be produced in a simple and cost-effective manner.

In example embodiments, the ring is provided in a groove, in particularin a groove in the housing of the gear unit that extends around in thecircumferential direction. It is advantageous in this regard that theminimum oil level is specifiable in a simple manner. Although such aring does not provide as a high a protection against spraying oil as theuse of a protective plate, it offers a simple manner of ensuring theminimum oil level.

In example embodiments, the cutout encloses the traversing shaft astightly as possible, in particular at a distance of less than 3 mm, inparticular of less than 1 mm. It is advantageous in this regard that amaximum protection against spraying oil or oil foam is achievable.

In example embodiments, the protective plate is flat, in particularcovers the area of the cutout for the bearing. It is advantageous inthis regard that a simple sheet-metal stamped part may be used, in whichonly the outer contour and the cutouts for the passage of shafts, inparticular semicircular cutouts provided in the edge region of theprotective plate, are required.

In example embodiments, the housing of the gear unit includes a lowerand an upper housing part, the assembly of the gear unit being verysimple and not requiring much effort,

a protective plate being fastened on the lower housing part, whichsubstantially surrounds the lower half of the shaft,

another protective plate being fastened on the upper housing part, whichsubstantially surrounds the upper half of the shaft. It is advantageousin this regard that the insertion of a ring or of a protective plate isparticularly simple. Components such as bearings, shafts and gear wheelsare also mountable in a simple manner. For these are simply insertedfrom above into the corresponding receiving area. In the case of a ring,the receiving area is a groove running in the circumferential direction.The protective plate by contrast is insertable from above and may thenbe pressed against the housing wall. Subsequently, a welded and/orscrewed connection may be performed.

In example embodiments, a bearing is provided in one housing part of thegear unit for supporting the input shaft,

a fan impeller being provided on the input shaft,

the housing part being slanted at least in the surface area adjacent tothe fan impeller and/or a slanted hood being attached to the housingpart.

It is advantageous in this regard that the cooling air flow is able tobe guided as well as possible and that therefore a greatest possibleportion of the air flow flows along the housing. In this manner, apowerful cooling air flow capable of dissipating heat from the gear unitis producible by a fan impeller that is driven passively, that is,without a separate motive drive, and a great output is producible perunit volume.

In example embodiments, cooling fins are provided on the slanted area ofthe housing part or on the hood. It is advantageous in this regard thatthe surface is enlarged and thus an improved heat dissipation isensured. In particular, the heat from the housing may thus be conductedvia air to the hood and from their to the surroundings. In addition, theslanted housing part or the slanted hood acts as an air guide elementand reduces turbulence.

In example embodiments, cooling fins and/or cooling fingers are providedon the housing part of the gear unit. It is advantageous in this regardthat the surface is enlarged. In the case of cooling fingers, it is evenpossible to achieve an isotropic heat dissipation, that is, a heatdissipation that is independent of the installation orientation of thegear unit.

In example embodiments, a housing cover is provided on the housing ofthe gear unit, which is tightly connectable to one housing part andwhich has cooling fins on its outside. It is advantageous in this regardthat a large opening is provided in the housing of the gear unit forinstallation, maintenance or for an oil change.

In example embodiments, the cooling fins are oriented according to thedirection of the cooling air flow, the cooling fins in particular beingoriented in parallel to one another. It is advantageous in this regardthat the air flow may be configured in a suitable manner and that inparticular an air guide function is implementable.

In example embodiments, the input gear stage is a right-angle gearstage. It is advantageous in this regard that a slanted housing may beprovided and thus an improved air guide function may be achieved.

In example embodiments, an air guide encasement is provided around thegear unit. It is advantageous in this regard that the cooling air flowmay be guided through between the gear unit housing and the encasementand thus a very good utilization of the cooling air flow is achievablein a simple manner. In addition, another protection is provided for thegear unit housing, in particular for bearing covers, screw plugs and/oroil drain plugs and the like. Such parts may thus also be implemented inplastic instead of steel or cast steel since the encasement may beimplemented from sheet steel and thus a metallic protection is providedagainst the surroundings.

In example embodiments, the air guide encasement guides the cooling airflow and limits it together with the cooling fins and the housing of thegear unit to the spatial region provided for the cooling air flow, inparticular in such a way that the cooling air flow takes up as muchthermal output of the gear unit as possible. It is advantageous in thisregard that the air flow may be guided in such a way that the air flowis able to dissipate the heat of the housing as much as possible.

In example embodiments, the air guide encasement has passages for theinput and output shaft and for setting up the gear unit on the floor,the air guide encasement in particular having additionally only one morecutout for a sensor. It is advantageous in this regard that the cutoutsmay be implemented in a simple manner, that is, it is not necessary toimplement them in a sealed manner.

In example embodiments, a pipe is provided for conducting oil out of theinterior of the gear unit into the area of the cooling air flow, and apipe for guiding the oil back into the interior of the gear unit islikewise provided in the area of the cooling air flow, the lines inparticular being situated entirely or at least in part in the coolingair flow produced by the fan impeller. It is advantageous in this regardthat a cooling of the oil of the gear unit is achievable in a simplemanner. In particular, all that is required is for the oil in a pipe tobe conducted out and back in again.

In example embodiments, the oil transported out via the pipe is suppliedto a plate-type cooler, which is situated on the housing of the gearunit, in particular in the cooling air flow, the pipe for returning theoil in particular transporting oil from the plate-type cooler back intothe interior of the gear unit. It is advantageous in this regard that animproved heat dissipation may be achieved, the plate-type cooler beingin particular able to be disposed in the cooling air flow and thus ableto be cooled passively. Via a meander-shaped routing in the plate-typecooler, the oil flow is in contact with the plate-type cooler for a verylong time and is thus able to give off the greatest possible heat flowto the air.

In example embodiments, the oil level, in particular of the oil sump ofthe gear unit, is lower in operation than the oil level at a permanentstandstill of the gear unit, a device being provided in particular forlowering the operating oil level, the device for lowering being inparticular a device for the temporary storage of oil. It is advantageousin this regard that the bearing and toothed parts are well-drenched inoil when starting the gear unit since the oil level is initially veryhigh. In operation, that is, with the oil level lowered, splash lossesare reduced and a lubrication of the bearings or toothed parts isachievable from the temporary storage unit via other feeder devices.These feeder devices are operable in operation without representing anadditional energy loss of the gear unit.

In example embodiments, a temporary storage unit is provided, to whichoil may be supplied from the oil sump of the gear unit, in particularusing a feeder device, the temporary storage unit being in particularsituated in the interior of the gear unit, that is, being surrounded bythe gear unit housing in a housing-forming manner. It is advantageous inthis regard that no additional housing or additional space is requiredfor the temporary storage unit, but that rather the existing space inthe housing of the gear unit is utilizable. This particularly applies toa housing that surrounds the toothed parts substantially in the shape ofa rectangular parallelepiped, a slanted area being providable that ismounted onto the rectangular parallelepiped in the area of the inputshaft. Advantageously, a rectangular parallelepiped housing ismanufacturable simply and cost-effectively and has a high stability at alow wall thickness and a low usage of material. Thus a substantiallyrectangular parallelepiped interior is available minus the rotation areaof the toothed parts and the area of the shafts and bearings. Thisremaining space is utilizable as a temporary storage unit.

In example embodiments, the temporary storage unit is arranged as avessel, which has cutouts so as to be drainable through these cutouts.It is advantageous in this regard that the temporary storage unitempties when the gear unit is in the state of rest, in particular with afirst time constant. The feeder device in the gear unit fills thetemporary storage unit at such a feed rate that the transported oil flowwould fill the temporary storage unit at such a second time constant ifthe cutouts did not exist that this second time constant is smaller thanthe first time constant, in particular more than three times smaller oreven more than ten times smaller.

In example embodiments, the temporary storage unit is arranged as avessel, which has such cutouts, and the feeder device is arranged suchthat the maximum oil flow supplied by the feeder device, in particularwhen operating the gear unit at the nominal speed of the gear unit, isgreater than the return oil flow from the temporary storage unit to theoil sump, which is effected by the cutouts. It is advantageous in thisregard that the temporary storage unit may be filled quickly and thusthe oil level of the gear unit is lowered very quickly following thestart of operation. It is in particular advantageous to provide thecutouts to be so small and to provide the feeder device with such a feedrate that the supplied oil flow is at least three times or even tentimes greater than the returned oil flow.

In example embodiments, the temporary storage unit has an overflow, inparticular a height-adjustable overflow, via which excess oil may bedrained into the oil sump. It is advantageous in this regard that theoil level may be adapted depending on the variant of the gear unit. Inaddition, this allows for an adaptation of the lowered oil level as afunction of the operating conditions and manufacturing tolerances.

In example embodiments, the feeder device has a baffle plate forcollecting oil, oil dripping off the baffle plate being suppliable tothe temporary storage device via a drainage channel and/or a collectorchannel. It is advantageous in this regard that a part of the feederdevice is implementable in a simple manner and that oil sprayed aroundmay be readily captured.

In example embodiments, the drainage channel or collector channel has acutout, into which a pipe empties, from which a ball bearing and/ortoothing may be lubricated. It is advantageous in this regard that thefeeder devices are simple and cost-effective.

In example embodiments, the drainage channel is curved such that a firstportion of the oil dripping off the baffle plate and collecting in thedrainage channel flows into a first collector channel and a secondportion of the oil dripping off the baffle plate and collecting in thedrainage channel flows into a second collector channel, the temporarystorage unit being fillable from the collector channels and thecollector channels being situated axially on the side of one gear wheelof the gear unit. It is advantageous in this regard that the remainingspace that is not part of the area of rotation of the toothed parts andthat is provided in the interior of the rectangular parallelepiped gearunit become usable.

In example embodiments, at least a partial area of a toothed part of thegear unit is surrounded by a bowl such that oil is only able to sprayupward, the bowl in particular having a cutout on its bottom side so asto allow for the bowl to be filled from the oil sump, in particular whenthe gear unit is not in operation. It is advantageous in this regardthat more oil sprays off upwardly and thus an improved heat dissipationis achievable since the oil must travel a long way to the oil sump, itbeing in contact with the housing of the gear unit as it flows back.

In example embodiments, the feeder device includes an oil scrapingdevice, which allows oil to be scraped from the front of a rotating gearwheel and allows the scraped oil to be supplied to the temporary storageunit or to a collector channel via a pipe, the pipe in particular beingoriented upward, the gear wheel in particular being immersed at leastpartially in the oil sump, and the oil scraping device in particularbeing situated above the oil sump. It is advantageous in this regardthat another cost-effective and simple feeder device is providable. Itis possible in particular to achieve a feed effect so as to transportoil through the pipe into a collector device or a temporary storageunit, from which in turn a pipe leading into the surroundings may befed. It is thus possible to transport oil into the surroundings and todissipate the heat there in the cooling air flow, in particular usingthe plate-type cooler situated there.

In example embodiments, the pipe includes bores in the drive unithousing. It is advantageous in this regard that oil may be transportedthrough these bores to the bearings, ball bearings for example. Thismakes it possible to ensure the lubrication of these bearings.

In example embodiments, a feeder device transports oil from the interiorof the gear unit through a pipe, which is fastened on the outside of thegear unit, the pipe in particular returning the oil into the interior ofthe gear unit. It is advantageous in this regard that the oil may becooled in the outer area around the gear unit, in particular in acooling air flow that is driven by a fan impeller.

In example embodiments, the pipe has a downward slope on the outside ofthe gear unit, the oil in particular flowing from a collector device,such as a temporary storage unit or collector channel, situated in theinterior of the gear unit, through the pipe outwards and from there backinto the oil sump,

the collector device in particular being situated above the oil sump. Itis advantageous in this regard that the oil flow may be driven by themere downward slope in the gravitational field, that is, passively. Forthis purpose, an energy loss of the gear unit is utilized to raise theoil. For the oil in the interior of the gear unit is sprayed around inoperation, in particular also upwards. A portion of the oil collectedthere is then transported downward without an additional pump byutilizing the downward slope and is cooled in the process.

In example embodiments, the pipe provided on the outside conducts oil toa plate-type cooler, and another section of the pipe returns oil fromthe plate-type cooler back into the oil sump in the interior of the gearunit. It is advantageous in this regard that the oil may be transportedsimply and in a cost-effective manner.

In example embodiments, the plate-type cooler is fastened on the outsideof the gear unit and is situated in the cooling air flow. It isadvantageous in this regard that an enlarged surface is provided andthus an improved heat dissipation is achievable. In particular, theplate-type cooler may be oriented in parallel to the cooling air flowsuch that the flow displays as little turbulence as possible.

In example embodiments, the bearings, in particular the two bearings ofthe input shaft of the gear unit, are provided in one housing part, inparticular in a substantially pot-shaped housing part, the housing partbeing provided in a screwed connection with a housing part of the gearunit. It is advantageous in this regard that the installation of theinput shaft into a housing part may be prefabricated, that is,preassembled. Thus this unit comprising the input shaft, its bearingsand associated seal may be stored in a warehouse and installed quicklyand simply. In particular, it is also possible to produce a model lineof gear units that offers a high degree of variation with few parts. Forthe gear unit may be implemented as a parallel-shaft gear unit if theopening in the housing of the gear unit provided for the pot-shapedhousing part is closed and the input shaft is provided on an opening ofthe lateral wall of the gear unit. Alternatively, however, theright-angle gear stage may also be provided instead of the closing part.Thus a gear unit having an input right-angle gear stage or an inputparallel-shaft gear stage may be manufactured from the same basichousing.

In example embodiments, a first bearing is implementing as a pair ofbearings, a first interspace being formed in the axial direction betweenthe paired individual bearings. It is advantageous in this regard thatgreat lateral forces may be absorbed and thus a particularly stable gearunit may be manufactured. In particular, a pair of individual bearingsthat are angled against each other may be used, between the outer ringsof which an interspace is thus produced.

In example embodiments, a second bearing is axially distanced from thefirst bearing so as to form a second interspace. It is advantageous inthis regard that great lateral forces may again be absorbed. The greaterthe distance between the bearings, the greater the lateral forces thatcan be absorbed.

In example embodiments, a first bearing of the input shaft is arrangedas a pair of tapered roller bearings that are angled against each other,in particular in an X arrangement, and a second bearing is arranged as aswiveling roller bearing. It is advantageous in this regard that aparticularly stable system is producible that is able to accommodatelateral forces.

In example embodiments, the first and/or second interspace are connectedto the interior of the gear unit by one or more bores, in particular fordrainage. It is advantageous in this regard that a good lubrication isachievable when the gear unit is at rest. It is advantageous for thispurpose to provide the oil level of the gear unit to be appropriatelyhigh in the state of rest or to provide the position and the downwardslope of the bores to be appropriately low. When the gear unit is inoperation, it is possible to maintain a minimum oil level in theinterspaces again by an appropriate definition of the height of thebores and of the downward slope. In particular, bores without a downwardslope may also be used advantageously. Another advantage of draining theinterspaces is that no great oil quantities are permanently present onthe input-side seal and thus it is possible to reduce the danger of oilescaping.

In example embodiments, the first and/or second interspace is connectedto the interior of the gear unit by a gap, in particular for drainage,the gap being formed between the housing part, in particular thesubstantially pot-shaped housing part, and the housing part of the gearunit. It is advantageous in this regard that a passage for oil may beprovided in a simple manner and thus the interspace may be emptiedwithout additional expenditure.

In example embodiments, a bore or one of the bores is a radial bore. Itis advantageous in this regard that a simple and inexpensive bore may beprovided for drainage. In particular, this bore may be disposed in thedirection of gravity such that drainage may be achieved in aparticularly effective manner. A horizontal orientation of the bore isalso advantageous, however, for maintaining a minimum oil level.

In example embodiments, a bore or one of the bores is an axiallyoriented bore. It is advantageous in this regard that a drainage to theoil sump located axially further inward may be achieved with littleexpenditure.

In example embodiments, the radial bore is provided to be closed on itsouter end by a sealing plug. It is advantageous in this regard that notonly is a simple and cost-effective radial bore sufficient for drainage,but that an access to the area of the bearings is created as well. Thussensors, for example for determining the speed of the input shaft, thelateral force or the axial force, may be situated in the area of thebearings, or also sensors for monitoring the functioning of the bearingssuch as temperature sensors or structure-borne noise sensors. Theassociated signal lines are able to be conducted out through the radialbore and the accordingly tightly closing sealing plug without particulareffort.

In example embodiments, an input shaft is provided to be sealed againstthe housing part, in particular against the pot-shaped housing part, bya shaft sealing ring. It is advantageous in this regard that oil may beprevented from escaping.

In example embodiments, the height of the bore or of the gap fordraining an interspace determines a minimum oil level for the bearingsof the input shaft. It is advantageous in this regard that the minimumoil level may be maintained in a simple manner with little expenditure.

LIST OF REFERENCE NUMERALS

-   1 Housing part-   2 Fan impeller-   3 Cooling fins-   4 Housing cover with cooling fins-   5 Cooling fins of the housing cover 4-   6 Cooling fins on the slanted housing part-   7 Output shaft-   8 Slanted housing area for the right-angle gear stage-   9 Cooling fins-   41 Rotary flange part, connected to output shaft 7 in a rotationally    fixed manner-   42 Air guide encasement-   50 Drain pipe-   51 Feed pipe-   52 Plate-type cooler-   53 Drain pipe-   60 Feed pipe-   61 Feed pipe-   62 Drain pipe-   70 Operating level of the oil-   71 Standstill level of the oil-   72 Bearing-   73 Bowl for tapered gear wheel-   74 Bowl for bevel pinion-   80 Temporary storage unit-   90 Lateral collector pockets-   91 Drainage opening for bearing lubrication-   92 Baffle plate-   93 Oil guide channel-   100 Pipe-   101 Scraper-   120 Gear wheel-   130 Roof-shaped housing cover-   131 Protective plate-   132 Overflow-   151 Housing cover-   160 Gear unit housing-   161 Gap-   162 Swiveling roller bearing-   163 Gap-   164 Bore-   165 Housing part, pot-shaped-   166 Tapered roller bearings angled against each other in an X    arrangement-   167 Flange part-   168 Shaft sealing ring-   169 Interspace area between the two tapered roller bearings-   170 Bore, radial-   171 Sealing plug-   172 Interspace area-   173 Bore, axial

Example embodiments of the present invention are explained in greaterdetail with reference to the Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front view of a first gear unit of an example embodimentof the present invention.

FIGS. 2 and 3 show the gear unit as shown in FIG. 1 from two differentdirections.

FIG. 4 shows another gear unit according to an example embodiment of thepresent invention, an encasement being additionally provided in contrastto FIGS. 1 through 3.

FIG. 5 shows another gear unit according to an example embodiment of thepresent invention having a plate-type cooler 52, which is fastened tothe housing of the gear unit.

FIG. 6 shows another gear unit according to an example embodiment of thepresent invention, oil lines being shown that lead out of the interiorof the gear unit and back into it.

FIG. 7 shows a lateral view of another gear unit according to an exampleembodiment of the present invention, which is shown in a section along alateral surface, the oil level being shown in operation and at astandstill.

FIG. 8 shows a corresponding oblique view, in which guide channels 93and a collector pocket 90 may be seen as well.

FIG. 9 shows a top view, that is, a view from above, of the gear unitfrom FIG. 7, which is likewise shown in a section, the section havingbeen cut on the top side.

FIG. 10 shows a scraping element belonging to the oil feeder device.

FIG. 11 shows the scraping element in an oblique view.

FIG. 12 shows the scraping element in a top view.

FIG. 13 shows protective plates 132 against spraying oil.

FIG. 14 shows protective plates 132 separately, these being connected tothe gear unit housing.

FIG. 15 shows a housing cover 151 that has a roof-like shape.

FIG. 16 shows a horizontal cross section through the input right-anglegear stage.

FIG. 17 shows a top view in a similar section.

FIG. 18 shows the view from another viewing direction.

DETAILED DESCRIPTION

In the exemplary embodiment shown in FIGS. 1 through 3, a fan impeller 2is connected on the input shaft in a rotationally fixed manner. The fanimpeller is thus operated at a suitably high rotational speed andproduces a powerful air flow using its fan impeller vanes when the gearunit is operated at the nominal rotational speed. The higher therotational speed and the torque, the higher is also the power loss, thatis, the thermal power to be dissipated to the surroundings.

The cooling air flow produced by fan impeller 2 is conducted along aslanted housing area 8. This is either produced by mounting suitablyformed pieces of sheet metal and connecting them to housing part 1 oralternatively by forming housing part 1 suitably, which may beaccomplished without special additional effort particularly in the caseof an input right-angle gear stage.

Furthermore, cooling fins 6 are provided on slanted housing area 8 andcooling fins 3 and 9 on housing part 1.

A housing cover 4 having cooling fins 5 is also provided on the housingpart for mounting and maintenance purposes.

In this manner, the cooling air flow may be utilized in optimizedfashion.

Output shaft 7 is developed on two sides, but may also be arranged onone side only in other exemplary embodiments.

In FIG. 4, an additional air guide part, that is, an air guideencasement 42 is provided on the gear unit. A passage is provided forinput shaft and output shaft 7. In another contrast to FIGS. 1 through3, output shaft 7 is connected to a rotary flange part 41 in arotationally fixed manner.

Air guide encasement 42 reduces the tendency of the cooling air flow todrift off and thus results in a more powerful heat dissipation. Inaddition, it also serves to protect against dust deposits on the gearunit housing and thus protects against a deterioration of the heattransfer resistance from the gear unit housing to the cooling air flow.

Moreover, additional parts or components to be cooled may be disposedbetween the gear unit housing and the air guide encasement such as powerelectronics or cooling devices for cooling oil for example. Thesubsequent figures describe exemplary embodiments of the latter.

In FIG. 5, a plate-type cooler 52 is fastened to housing 1 of the gearunit, which has oil supplied to it from the interior of the gear unitvia one or multiple feed pipes 50 and from which oil is removed via oneor more drain pipes 51. The plate-type cooler preferably includes a baseplate having a meander-shaped groove, a cover plate being mounted on thebase plate. The oil must thus flow through the plate-type cooler inmeander-shaped fashion. Alternatively, straight bores may also beimplemented in a base body and the oil may be conducted through thebores, diverting pieces being provided between the end areas of thebores on the base body.

On the rear side with respect to the side of the gear unit having theplate-type cooler, thus the side not visible in FIG. 5, a plate-typecooler 52 having the corresponding pipes may likewise be provided, sothat a doubling of the cooling capacity is attainable.

Plate-type cooler 52 is omitted in FIG. 6. Feed pipes 60 and 61 aremerged and open out into drain pipe 62. The pipes are thus directlyexposed to the cooling air flow, and a sufficient cooling power may beachieved even without the expenditure of a plate-type cooler,particularly if oil flows through slowly.

FIG. 7 shows that operating level 70 of the oil is lower compared to thestandstill level 71 of the oil. As the gear unit starts up, a goodlubrication of all bearings is thus immediately provided, in particularalso of the bearings of the input gear stage or bearings 72 of one ormore of the intermediate stages of the gear unit since the oil level isso high that the bearings and toothed parts are situated sufficientlydeeply in the oil sump. If the gear unit is thus started even after longperiods of standstill, a good lubrication is provided.

The input stage of the gear unit is arranged as a right-angle gearstage. For this purpose, a bevel pinion is provided on the input shaft,which mates with a tapered gear wheel. Splash losses are reduced by abowl 73 for the tapered gear wheel and a bowl 74 for the bevel pinion,which are respectively provided around the lower half of these toothedwheels. For the bowls (73, 74) are shaped such that the oil at least inthe area of the bowls (73, 74) is essentially kept on a circular pathwhen the toothed parts are rotating. The inner area between therespective bowl and the toothed part is thus freed of oil or the levelof oil is at least substantially reduced in this area.

Since the bowls (73, 74) essentially surround only the lower half of thetoothed parts, oil sprays only upward. Hence, when running off by theforce of gravitation, the oil must traverse long paths along the innersurface of the housing and/or along a feed system, which makes itpossible to achieve a good heat transfer from the oil to the gear unithousing. The bowls (73, 74) have on their lower side at least one cutoutsuch that oil may be replenished from the oil sump into the spacebetween the bowl (73, 74) and toothed part. However, the cutout is sosmall that the oil flow into the space is at least five times or atleast ten times smaller than the oil flow which the toothed part is ableto transport out of the space when the nominal speed of the input shaftis reached in operation.

The bowls (73, 74) are preferably arranged in a half-torus shape.

As shown more clearly in FIG. 8, oil is transported in operation into ahigher temporary storage unit 80 using the oil feed system described inmore detail below such that the oil level decreases. This lowering ofthe oil level in operation makes it possible to achieve a reduction ofsplash losses. That is to say that the toothed parts enter the oil sumponly to a small extent, the quickly rotating toothed parts inparticular, such as the toothed parts of the input gear stage and of oneor more intermediate gear stages for example, dip less deeply or not atall into the oil sump.

Intermediate storage unit 80 has leakages or otherwise especiallyprovided small cutouts such that the temporary storage unit emptiesautomatically. The cutouts are provided such that in nominal operationthe oil level is lowered as intended, that is, the oil flow flowing intotemporary storage unit 80 is greater than the oil flow that flows backfrom temporary storage unit 80 into the oil sump—at least until the oillevel in the temporary storage unit is below a critical value.

Thus the temporary storage unit is filled in operation using the oilfeed system, and thus the oil level in the gear unit, in particular inthe oil sump, is lowered as the oil level rises in temporary storageunit 80 such that the power losses are reduced.

In operation, the bearings and toothings are lubricated in that the oilpressed and/or sprayed out of the engaged toothings is collected bybaffle plates 92 and drips from the latter into oil guide channels 93,which fill lateral collector pockets, from which at least a portion ofthe collected oil is fed to the bearings and toothed parts to belubricated.

As shown in FIG. 9, for this purpose, the collector pockets 90 situatedon both sides in the gear unit have drainage openings 91 for bearinglubrication. The drainage openings open out into bores in the housing,through which the oil is conducted to the bearing to be lubricated orvia guide channels to the respective toothed part to be lubricated.

Oil guide channels 93 are arranged in a bent fashion such that oneportion of the collected oil is conducted into a first and anotherportion into the other collector pocket 90.

It is not necessary in every case to lubricate the toothed parts and thebearings of the output shaft since these toothed parts turn slowly andthus produce only small splash losses. An immersion of these toothedparts and bearings into the oil sump is therefore not harmful.

Baffle plates 92 and oil guide channels 93 are preferably fastened onthe top side of the gear unit housing.

The drain openings are situated in collector pockets 90 and thecollector pockets are arranged such that the oil that arrives first whenstarting the gear unit is used for lubricating the bearings or toothedparts. Temporary storage unit 80 will be filled only when the collectedoil flow exceeds this oil flow required for lubrication.

In another exemplary embodiment, intermediate storage unit 80 preferablyhas an adjustable overflow. For this purpose, a horizontal cutout may beprovided in a lateral wall of temporary storage unit 80, which may becovered by a sheet metal cover piece capable of sliding in thehorizontal direction. The overflow height and thus also the maximumvolume of temporary storage unit 80 is thus adjustable by sliding thesheet metal cover piece.

FIG. 10 shows another oil feeder device, featuring a scraper 101, whichscrapes off oil on a front of a gear wheel and presses it into pipe 100,from which lateral collector pockets 90 may be filled. The oil feederdevice described above, including oil guide channel 93, is additionallyeffective. In this manner it is possible to collect oil accumulating onthe gear wheel and sprayed around by the gear wheel and to use it forlubricating bearings or for lowering the oil level in operation.

Scraper 101 together with pipe 100 are shown separately in FIG. 11. Hereit may be seen more readily that the scraper has a V-shaped cutout, atthe pointed end of which a bore is provided, into which pipe 100 opensout.

FIG. 12 shows the arrangement of scraper 101 on gear wheel 120.

FIG. 13 shows another gear unit, in which, in contrast to the figuresdescribed above, a roof-shaped housing cover 130 is provided in place ofhousing cover 4. Oil dripping off the inner side of this roof-shapedhousing cover may then be conducted into collector pockets 90 via oilguide channels 93. In this manner it is possible to collect and use—notthe oil centrifuged in the horizontal direction as in the case of thebaffle plate—but the oil centrifuged in the vertical direction againstthe inner side of roof-shaped housing part 130.

FIG. 15 shows a housing cover 151, which is developed in a V shape, thatis, roof shape, the point of the V pointing upwards. The angle of theroof area, that is, the angle of the respective leg of the V to thehorizontal, is greater than 10°. The angle is preferably selected suchthat the drops sprayed onto the inside of the roof-shaped housing covermove laterally downward on the slope of the roof under the influence ofgravity, the drops being adhesively bound to the cover and then drippinginto oil guide channels 93. The angle is thus always selected such thatfor drops sticking adhesively to the surface the force of gravitation issmaller than the adhesive force. The angle also depends substantially onthe surface tension between the oil and housing cover 151.

FIG. 13 also shows protective plate 131, which is used to protect ballbearings against spraying oil or against oil foam driven in thedirection of the ball bearings. Protective plate 131 is arranged to beso wide that even multiple ball bearings may be protected, in particularthe ball bearing of the input shaft, an intermediate shaft and/or outputshaft 7. Protective plate 131 is fastened to the inner side of thehousing and has cutouts of such a size that the rotatably supportedparts associated with the respective ball bearings do not touchprotective plate 131.

In FIG. 13, a distance sleeve is attached on the shaft between the gearwheel and the associated ball bearing for maintaining a defined distancebetween the ball bearing and the gear wheel. The distance sleeve is thusprovided in a cutout of protective plate 131.

Protective plate 131 has an overflow 132 such that oil from the oil sumparrives in the area of the protected ball bearings when the oil level ofthe oil sump is higher than the overflow, in particular the overflowedge.

Protective plate 131 is welded or screwed to the inner side of thehousing such that the ball bearings are immersed in oil. Especially alsoin operation, that is, when the oil level falls in the oil sump, aminimum oil level still exists around the ball bearing. It isfurthermore advantageous in this regard that the oil supplied to thetoothed parts via the feeder device collects in the space around theball bearing that is at least partially bounded by protective plate 131,a drainage of the oil being provided if the minimum oil level around theball bearing rises above overflow 132.

FIG. 14 shows the embodiment with protective plate 131 in more detail.For this purpose, a lower and an upper protective plate 131 are used,the housing of the gear unit being likewise divided into a lower and anupper housing part. Lower protective plate 131 is fastened to the lowerhousing part, while upper protective plate 131 is fastened to the upperhousing part, in particular screwed, as shown in FIG. 14, or welded, asin an alternative exemplary embodiment.

An alternative exemplary embodiment provides, instead of protectiveplate 131, a ring inserted into a groove, which thus defines an overflowby the lowest enclosed point. Although the ring is then not able torepresent a substantial spray protection, it is able to implement thefunction of the overflow.

In another exemplary embodiment, a previously mentioned protective plateis used for a first bearing, while the aforementioned ring is used foranother bearing.

The exemplary embodiment shown in FIGS. 16, 17 and 18 shows the inputright-angle gear stage in more detail. This is arranged as a taperedgear stage.

At the axial end, a pot-shaped housing part 165 is screwed onto gearunit housing 160, to which in turn a flange part 167 is screwed, whichreceives a shaft sealing ring 168 that seals the interior of the gearunit against the outer surroundings.

In pot-shaped housing part 165, two tapered roller bearings 166 areprovided angled against each other in an X arrangement, the axialdistance between them producing interspace area 169. This interspacearea 169 is thus bounded by the two tapered roller bearings 166 and bypot-shaped housing part 165.

When the gear unit is not in operation and the oil level is thereforehigh, interspace area 169 is at least partially filled with oil sincethe latter runs into it from the interior of the gear unit. Inoperation, the oil level of the oil sump in the gear unit is lowered.Interspace area 169 is drained via a radial bore 170, which opens outinto interspace 169 and which is closed on its outer radial end by asealing plug 171. An axial bore 173 leads from radial bore 170 back intothe interior of the gear unit. The positioning of the bores,particularly the provided height relative to the oil sump, makes itpossible to maintain a defined minimum oil level in interspace area 169.Draining interspace area 169 down to this minimum oil level results in areduction of losses since the bearings are then less surrounded by theoil.

Another interspace area 172 between the tapered roller bearing 166situated axially further inside and the swiveling roller bearing 162,via which the input shaft is supported in pot-shaped housing part 165,is drained in an analogous manner. Radial bore 164 is provided for thispurpose, which empties into a gap 163 leading axially inward andsituated between housing 160 of the gear unit and pot-shaped housingpart 165, which gap widens in the axial inward direction into a gap 161.

On its axially inward end, input shaft bears the bevel pinion, whichmates with a tapered gear wheel that is supported by bearings providedin housing 160 of the gear unit.

The invention claimed is:
 1. A gear unit, comprising: more than oneshaft each supported by a respective bearing in a gear unit housing;wherein a spatial region of each of the more than one shaft bearings aresituated in a cutout of the gear unit housing is limited at leastpartially with respect to an interior of the gear unit by a limitingdevice that has a cutout for each of the more than one shaft supportedin the respective bearings, a lowest point of the respective cutoutseffecting a minimum oil level in the spatial region of each of the morethan one shaft bearing; wherein the limiting device includes a lowerprotective plate being fastened on the housing part, which directly andsubstantially surrounds a lower half of each of the more than oneshafts, and an upper protective plate being fastened on the housingpart, which directly and substantially surrounds an upper half of eachof the more than one shafts; and wherein the lower and upper protectiveplates are flat and cover an area of the respective cutouts for thebearings.
 2. The gear unit according to claim 1, wherein the cutout isat least one of (a) substantially semicircular and (b) substantiallycircular.
 3. The gear unit according to claim 1, wherein the spatialregion is limited at least partially by the gear unit housing.
 4. Thegear unit according to claim 1, wherein the limiting device includes aring.
 5. The gear unit according to claim 4, wherein the lower and upperprotective plates are at least one of (a) welded and (b) screwed ontothe housing.
 6. The gear unit according to claim 4, wherein the ring isprovided in a groove in the housing of the gear unit that extends aroundthe housing of the gear unit.
 7. The gear unit according to claim 1,wherein the cutouts enclose each of the more than one shaft as tightlyas possible, a distance of at least one of (a) less than 3 mm and (b)less than 1 mm.
 8. The gear unit according to claim 1, wherein one ofthe more than one bearings is adapted to support an input shaft and isprovided in an area of a housing part of the gear unit, a fan impellerbeing provided on the input shaft, at least one of (a) a slanted area ofthe housing part at least in a surface area adjacent to the fan impellerand (b) a slanted hood being attached to the area of the housing part.9. The gear unit according to claim 8, wherein cooling fins are providedon at least one of (a) the slanted area of the housing part and (b) theslanted hood.
 10. The gear unit according to claim 1, wherein coolingfins are provided on the housing part of the gear unit.
 11. The gearunit according to claim 1, wherein a housing cover which is tightlyconnected to an area of the housing part, and which has cooling fins onan outside.
 12. The gear unit according to claim 11, wherein the coolingfins are oriented according to a direction of a cooling air flow and areoriented in parallel to one another.
 13. The gear unit according toclaim 1, wherein an input gear stage is a right-angle gear stage. 14.The gear unit according to claim 1, wherein an air guide encasement isprovided around the gear unit.
 15. The gear unit according to claim 14,wherein the air guide encasement is adapted to guide a cooling air flowand limit it together with cooling fins and the housing of the gearunit, so that the cooling air flow absorbs thermal output of the gearunit.
 16. The gear unit according to claim 14, wherein the air guideencasement includes passages for input shaft and an output shaft and forarranging the gear unit on a floor, the air guide encasement furthermorehaving at least one cutout for a sensor.
 17. The gear unit according toclaim 1, wherein a first pipe is provided to conduct oil out of aninterior of the gear unit into an area of a cooling air flow and asecond pipe to guide the oil back into the interior of the gear unit,the first and second pipes being arranged at least partially in thecooling air flow.
 18. The gear unit according to claim 17, wherein apart of the first pipe conducted out of the interior of the gear unit issituated between the gear unit housing and an encasement.
 19. The gearunit according to claim 17, wherein the oil transported by the firstpipe to conduct the oil out of the interior is suppliable to a platecooler, which is situated on the housing of the gear unit, in thecooling air flow, the second pipe adapted to return the oil beingadapted to transport oil from the plate cooler back into the interior ofthe gear unit.
 20. The gear unit according to claim 1, wherein an oillevel in an oil sump of the gear unit is lower in operation than an oillevel at a permanent standstill of the gear unit, and the gear unitincluding a temporary storage device being provided to lower theoperating oil level.
 21. The gear unit according to claim 1, wherein atemporary storage unit is provided, to which oil is suppliable from anoil sump of the gear unit, using a feeder device, the temporary storageunit being arranged in an interior of the gear unit and surrounded bythe gear unit housing.
 22. The gear unit according to claim 21, whereinthe temporary storage unit is arranged as a vessel, which has cutouts soas to be drainable through the cutouts.
 23. The gear unit according toclaim 21, wherein the temporary storage unit is arranged as a vessel,which has cutouts, and the feeder device is arranged such that a maximumoil flow supplied by the feeder device, when operating the gear unit ata nominal speed of the gear unit, is greater than a return oil flow fromthe temporary storage unit to the oil sump, which is effected by thecutouts.
 24. The gear unit according to claim 21, wherein the temporarystorage unit includes a height-adjustable overflow, via which excess oilis drainable into the oil sump.
 25. The gear unit according to claim 21,wherein the feeder device includes a baffle plate adapted to collectoil, oil dripping off the baffle plate being suppliable to the temporarystorage device via at least one of (a) a drainage channel and (b) acollector channel.
 26. The gear unit according to claim 25, wherein atleast one of (a) the drainage channel and (b) the collector channel hasa cutout, into which a pipe opens out, from which at least one of (a) aball bearing and (b) a toothing is lubricatable.
 27. The gear unitaccording to claim 25, wherein the drainage channel is curved such thata first portion of oil dripping off the baffle plate and collecting inthe drainage channel flows into a first collector channel and a secondportion of oil dripping off the baffle plate and collecting in thedrainage channel flows into a second collector channel, the temporarystorage unit being fillable from the collector channels and thecollector channels being situated axially on a side of one gear wheel ofthe gear unit.
 28. The gear unit according to claim 1, wherein at leasta partial area of a toothed part of the gear unit is surrounded by abowl such that oil is only able to spray upwards, the bowl having acutout on a bottom side so as to allow for the bowl to be filled from anoil sump, when the gear unit is not in operation.
 29. The gear unitaccording to claim 25, wherein the feeder device includes an oilscraping device, adapted to scrape oil from a front of a rotating gearwheel and adapted to supply the scraped oil to at least one of (a) thetemporary storage unit and (b) a collector channel via a pipe, the pipebeing oriented upwardly, the gear wheel being immersed at leastpartially in the oil sump, and the oil scraping device being situatedabove the oil sump.
 30. The gear unit according to claim 29, wherein thepipe includes bores in the gear unit housing.
 31. The gear unitaccording to claim 25, wherein the feeder device is adapted to transportoil from the interior of the gear unit through a pipe, which is fastenedon an outside of the gear unit, the pipe adapted to return oil into theinterior of the gear unit.
 32. The gear unit according to claim 31,wherein the pipe on the outside of the gear unit has a downward slope,the oil flowing from at least one of (a) a collector device, (b) atemporary storage unit, and (c) a collector channel, situated in theinterior of the gear unit, through the pipe to the outside and fromthere back into the oil sump, the collector device being situated abovethe oil sump.
 33. The gear unit according to claim 31, wherein the pipeprovided on the outside is adapted to conduct oil to a plate cooler, andanother section of the pipe is adapted to return oil from the platecooler back into the oil sump in the interior of the gear unit.
 34. Thegear unit according to claim 33, wherein the plate cooler is fastened onthe outside of the gear unit and is arranged in a cooling air flow. 35.The gear unit according to claim 29, wherein the oil scraping deviceincludes at least one of (a) a cutout, (b) an interior space, and (c) ahollow space, tapering in a direction of movement of oil to be scrapedfrom the front of the rotatably supported gear wheel, at an end area ofwhich the pipe is provided into which the scraped oil is pressed. 36.The gear unit according to claim 35, wherein the pipe situated on theoil scraping device extends upwardly.
 37. The gear unit according toclaim 36, wherein an upper end of the pipe situated on the oil scrapingdevice is connected one of (a) directly and (b) indirectly to a pipeadapted to conduct the oil at least one of (i) out of the interior and(ii) a temporary storage unit.
 38. The gear unit according to claim 1,wherein two bearings of the more than one shaft of the gear unit areprovided in a substantially pot-shaped housing part, the housing partbeing provided in a screwed connection with the housing part of the gearunit.
 39. The gear unit according to claim 38, wherein a first bearingis arranged as a pair of bearings, a first interspace being formed in anaxial direction between the paired individual bearings.
 40. The gearunit according to claim 39, wherein a second bearing is axiallydistanced from the first bearing so as to form a second interspace. 41.The gear unit according to claim 1, wherein a first bearing of the inputshaft is arranged as pair of tapered roller bearings that are angledagainst each other, in an X arrangement, and a second bearing isarranged as a swiveling roller bearing.
 42. The gear unit according toclaim 40, wherein at least one of (a) the first interspace and (b) thesecond interspace is connected to the interior of the gear unit by atleast one bore for drainage.
 43. The gear unit according to claim 39,wherein at least one of (a) the first interspace and (b) the secondinterspace is connected to the interior of the gear unit by a gap fordrainage, the gap being formed between a substantially pot-shapedhousing part and the housing part of the gear unit.
 44. The gear unitaccording to claim 42, wherein at least one bore is arranged as a radialbore.
 45. The gear unit according to claim 42, wherein at least one boreis arranged as an axially oriented bore.
 46. The gear unit according toclaim 44, wherein the radial bore is closed on an outer end by a sealingplug.
 47. The gear unit according to claim 1, wherein an input shaft issealed against a substantially pot-shaped housing part by a shaftsealing ring.
 48. The gear unit according to claim 42, wherein a heightof the bore for draining an interspace determines a minimum oil levelfor the bearings of the input shaft.
 49. The gear unit according toclaim 1, wherein the housing of the gear unit includes a lower housingpart and an upper housing part, the lower protective plate fastened onthe lower housing part, and the upper protective plate fastened on theupper housing part.